In relation to digital still cameras and video cameras, there has been proposed a solid-state imaging element wherein distance detection pixels having a distance detecting (focus detecting) function are used as pixels at part of or the whole part of the solid-state imaging element and wherein subject distance is detected by a phase difference system (see PTL 1).
The distance detection pixels are provided with a plurality of photodiodes as photoelectric conversion sections, and are configured in such a manner that light fluxes having passed through different exit pupil regions of an imaging lens are guided to different photodiodes. The photodiode has a function to generate an electric charge according to the amount of incident light by photoelectric conversion and to accumulate the electric charge during an imaging (exposure) time.
Here, by use of a plurality of distance detection pixels, images formed by light fluxes having passed through different exit pupil regions are detected (the images will hereinafter be referred to as image A and image B), and the deviation amount of image A and image B from each other is measured. A defocus amount is calculated from the deviation amount and a reference length (the spacing between the different exit pupil regions), and the distance (focal position) is detected. In this instance, an exit pupil plane of the imaging lens and a surface of the photodiode are in a substantially conjugate relation. Therefore, the exit pupil regions through which the light passes and light reception sensitivity are determined according to the positions and sizes of the photodiodes. Specifically, an increase in the size of the photodiode increases the exit pupil region through which the light passes, increases the amount of light received by the photodiode, and enhances sensitivity.
When the photodiodes of the distance detection pixels having a plurality of photodiodes are formed in a larger size, the proportion of the photodiodes in the distance detection pixels increases, and the distance between the photodiodes is reduced. When the distance between the photodiodes is reduced, an electric charge generated in the photodiode is liable to move to the other photodiode (electronic crosstalk). As a result, electric charge signals interfere with each other between the photodiodes in the distance detection pixels, and it becomes difficult to obtain correspondence between the electric charge signals of the photodiodes and the exit pupil regions through which light passes. Consequently, errors are generated in the deviation amount between image A and image B and in the reference length, which may lead to worsening of distance measurement accuracy.
In view of this problem, there has been proposed a technology in which the distance between the photodiodes is increased along the direction toward a bulk depth part, thereby to earn distance at a place where electron dwelling time is long and to restrain the electronic crosstalk (see PTL 2).